I'll play along. And since ggw chose Up To Here, I'll assume we can discount any EPs etc that came before the main debut CD/album.
1. Ten - Pearl Jam
2. Smeared - Sloan
3. Ben Folds Five - Ben Folds Five
4. Led Zeppelin - Led Zeppelin
5. Love Junk - The Pursuit of Happiness
I'm sure that there are more "worthy" CDs (like The Clash, Dylan, Ramones, The Who, etc) but these 5 CDs have all changed my life in some substantial way. Not bad for a band's first effort.